1. Field of the Invention
The present invention relates to an isotropic dry cleaning process for noble metal integrated circuit structures.
2. Description of the Related Art
Thin films of noble metals (Pt, Pd, Ir, Rh) have become technologically important in integrated circuits (ICs) as electrodes for ferroelectric and high .epsilon. thin films in FeRAMs, DRAMs, RF and microwave MMICs, pyroelectric IR focal plane detector arrays, etc.
The absence of viable dry etching techniques for submicron patterning of these electrodes is a chronic problem that has threatened to retard or even prevent widespread use of these materials. The present dry-etching approaches utilize plasmas for reactive ion etching (RIE), are chlorine-based, and result in significant residue being left on the microelectronic device structure after the etch process has been completed.
Depending on the type of structure that is being formed by the patterning, this post-etch residue may result in short circuiting, undesired topography or other deficiencies in the operation of the circuit element in subsequent use of the product microelectronic device. Prevention of the formation of such residues may be achieved in some instances by manipulating the reactive ion etching (RIE) process parameters, but such process manipulation results in undesirable sidewall slopes in the microelectronic device structure that effectively prevent useful submicron capacitors from being fabricated.
Alternatively, the residue resulting from RIE can be removed by wet rinsing techniques, after the etch process has been completed. Wet rinsing techniques are however generally unsatisfactory, because a significant fraction of the residue may be transported in suspension in the rinse media, allowing a small fraction of the residue solids to redeposit on the wafer, and thereby reducing device yield.
Further, in some microelectronic device structure geometries, the residue may not be removed using wet rinsing methods.
Another drawback of wet rinsing methods is the need for a separate process tool to implement the wet rinsing clean-up, which adds to the capital equipment and operating costs of the process system.
It would therefore be a significant advance in the art of integrated circuit device fabrication, in which noble metal films are formed on the device substrate as electrodes or other structural components of the device, to provide an effective cleaning process for removing unwanted residues on the integrated circuit structure after etching or other process fabrication steps.